1. Field of the Invention
This invention relates to wood burning heaters, and particularly to means for preventing flashes of flame from exiting its firebox door when that door is first opened.
2. General Description of the Prior Art
It is well known that when certain volatile woods are burned in a basically air-tight stove with a minimum draft setting, there is a tendency for a flame to flash out of the firebox door when it is first opened. It is believed that this occurs because of an initial differential in oxygen between that inside the stove and that outside the stove, there being, of course, more oxygen in the atmosphere just outside the stove than inside. To prevent this danger, stove manufacturers generally instruct owners to open wide the draft of the stove prior to opening the firebox door. Preferably, however, means would be provided to automatically supply added air (including oxygen) to the combustion chamber of the stove just prior to any opening of the firebox door. One such system is illustrated in U.S. Pat. No. 4,030,479. In accordance with this patent, an override is provided on an otherwise thermostatically controlled damper, causing the damper to be opened full "on" whenever the outer jacket door of a heater is opened, which is a necessary preparatory step to gaining access to the firebox door. This override is in the form of a rod which is curved to form a cam surface which, when the rod is moved longitudinally, operates the damper. The end of the rod is pivotally attached to the outer jacket door, and thus the opening of the outer door effects a withdrawal of the rod which causes the cam surface on the rod to effect an opening of the damper. In this fashion, it is insured that added air will be provided the firebox between the time that the outer jacket door opens and the time one can gain access to the firebox door. A difficulty with this arrangement is that it is somewhat complex and thus costly.
It is a feature of this invention to provide a system which is simpler and less expensive and yet provides a most effective means of curing the flashback problem.